Network Concepts. Networks LAN WAN Main Concepts n Protocol n Media n Topology.

Network Concepts

Networks

•LAN

•WAN

Main Concepts

ProtocolMediaTopology

Peer -to -Peer

ClientServer

ClientServer

ClientServer

Client/Server

Client ClientServer

Star - cableBus - signal

Star - cableRing - signal

Media

CoaxTwisted PairFiber OpticWireless

OSI Reference Model

7 Application6 Presentation5 Session4 Transport3 Network2 Data Link1 Physical

OSI Layers

• Physical– Signal encoding (voltage, amps, timing)– Connectors (BNC, RJ-45, ST)– Bit oriented

• Data Link– Frame oriented– Error detection– Media access control (token, CSMA/CD)

OSI

• Network– packet (datagram) oriented– Route data from network to network– Fragment and reassemble packets

• Transport– Reliable connection – ACK, NACK– Sequenced delivery– Flow control

OSI Layers

• Session– Logical connections

• Presentation– Character codes (EBCDIC vs. ASCII), encryption,

Compression (nice theory, usually done in other layers)

• Application– Like ftp, telnet, email, www, file and printer sharing

IEEE vs. OSI

LLCLogical Link Control

MACMedia Access Control

Physical

Data Link

Physical

OSI

IEEE

IEEE Standards

802.2 Logical Link Control802.3 CSMA/CD (Ethernet)802.4 Token Bus802.5 Token Ring

802.3

10Base5 10Base2 10BaseT 10BaseF

10Broad36 100BaseTX 1000BaseT

DIX

DigitalIntel

Xerox

Ethernet

IEEE vs. Ethernet Terminology

Ethernet IEEE 802.3

Station DTE - Data Terminal Equipment

Transceiver cable AUI - Attachment Unit Interface

Transceiver MAU - Medium Attachment Unit

Connector MDI - Medium Dependent Interface

Ethernet Frame

Preamble DestinationAddress

SourceAddress

Length/Type

LLC/Data

FrameCheck Sequence

Ethernet Frame


SourceAddress

Length/Type

LLC/Data

FrameCheck Sequence

64 bits of alternating ones and zeroes, for hardware synchronization, ending with twoones

Ethernet Frame


SourceAddress

Length/Type

LLC/Data

FrameCheck Sequence

48-bit address of station frameis being sent to

Ethernet Frame


SourceAddress

Length/Type

LLC/Data

FrameCheck Sequence

48-bit address of stationsending the frame

Ethernet Frame


SourceAddress

Length/Type

LLC/Data

FrameCheck Sequence

16-bit field, length of frame in 802.3, type of frame in DIX

Ethernet Frame


SourceAddress

Length/Type

LLC/Data

FrameCheck Sequence

46 to 1500 bytes of data, includes LLCfields in 802.3

Ethernet Frame


SourceAddress

Length/Type

LLC/Data

FrameCheck Sequence

32-bit cyclic redundancy check (CRC)code

Ethernet Addresses

48 bit normally shown in HEX

e.g.: 02-60-8C-44-59-E0 first 24 bits are obtained from IEEE by hardware manufacturers

one bit is used to distinguish unicast from multicast addresses

one bit is used to distinguish locally assigned addresses(rare) from globally assigned addresses (typical)

Transmission Types

Unicast - intended for one specific station Broadcast - intended for all stations Multicast - intended for a group of stations

CSMA/CD

Carrier Sense, Multiple Access with Collision Detection

Carrier sense - don't transmit if there is already a signal

Collision detection - if a collision is detected stop, wait, and retransmit

No Carrier

Transmission

End of Transmission

Transmission

Second Transmission

Collision

Collision detected

Repeater Hub

Repeater Hubone station transmits

Repeater Hubsignal repeated on all other ports

Repeater Hubend of transmission

Repeater Hub

Network Concepts. Networks LAN WAN Main Concepts n Protocol n Media n Topology.

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